The Specialists for Pectin - Herbstreith & Fox
The Specialists for Pectin - Herbstreith & Fox
The Specialists for Pectin - Herbstreith & Fox
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14<br />
<strong>The</strong> degree of<br />
esterification is determined<br />
by the type of<br />
chain association.<br />
<strong>The</strong> different Properties of <strong>Pectin</strong>s.<br />
Gell ing mech a nisms<br />
<strong>The</strong> as so ci a tion of pec tin chains leads to<br />
the <strong>for</strong> ma tion of three-di men sion al net -<br />
works, that is to gel <strong>for</strong> ma tion.<br />
<strong>The</strong>se are long seg ments of reg u lar<br />
sequence, rup tured by the in cor po ra tion<br />
of rham nose and branch ing of the chain.<br />
Two or more chain seg ments bond<br />
togeth er and start to inter act.<br />
Highesterpectins<br />
jel li fy pre dom i nant ly in the so- called<br />
“sug ar-ac id gell ing mech a nism”, that<br />
means a certain amount of ac id is re -<br />
quired to sup press the dis so ci a tion of the<br />
free car box yl groups. In this<br />
way, the neg a tive charg ing of<br />
the mole cules is pre vent ed<br />
and their mu tu al re pul sion re -<br />
duced.<br />
A high sug ar con cen tra tion<br />
low ers the wa ter ac tiv ity of the system,<br />
the pec tin mole cules are sub sequent ly<br />
de hy drat ed and clus ter more eas i ly in<br />
bond ing zones.<br />
galactan<br />
O<br />
GUS O GUS O<br />
RHA<br />
O<br />
O O O<br />
O GUS<br />
galactan<br />
O<br />
O<br />
RHA O GUS O GUS O GUS O GUS O GUS O<br />
RHA<br />
O<br />
O O O O O O O<br />
<strong>Pectin</strong> chain with galactan side chains<br />
Lowesterpectins,<br />
too, jel li fy in a sug ar-ac id gell ing mech anism.<br />
Pec tin mole cules with a low ester<br />
con tent, how ev er, may <strong>for</strong>m bond ing<br />
zones with bi va lent cat ions, but they may<br />
<strong>for</strong>m gels in rel a tive in de pen dence from<br />
soluble sol ids con tent and pH range in<br />
the pres ence of mul ti valent cat ions (e.g.<br />
cal cium ions).<br />
<strong>The</strong> cal cium con cen tra tion re quired <strong>for</strong><br />
gell ing de pends here on such pa ram<br />
e ters as pH of the prod uct, soluble<br />
sol ids con tent and buf fer system.<br />
With small er ad di tions of cal cium, pec tin<br />
chains will start to clus ter over cal cium<br />
bonds, the viscosity increases. With in -<br />
creased cal cium con cen tra tion, a gel will<br />
<strong>for</strong>m. Over dos age of cal cium ions will<br />
lead to cal cium pec ti nate pre cip i ta tion<br />
under the giv en gel <strong>for</strong>ma tion con di tions,<br />
this is al so called “pre-gell ing”.<br />
<strong>The</strong> gel struc ture will be less elas tic,<br />
rather pas ty with low er break ing strength.<br />
Precip i ta tion of cal cium pec ti nate is on ly<br />
re ver sible to a lim it ed ex tent, even when<br />
the gel is once more heat ed above its<br />
set ting tem per a ture and cooled down<br />
with out de struc tion.<br />
GUS = galacturonic acid<br />
RHA = rhamnose<br />
4<br />
OGUS<br />
O<br />
RHA O GUS O GUS<br />
O O O